Baskin Maria, Fridman Natalia, Kosa Monica, Maayan Galia
Schulich Faculty of Chemistry, Technion-Israel Institute of Technology, Haifa, 32000, Israel.
Dalton Trans. 2017 Nov 14;46(44):15330-15339. doi: 10.1039/c7dt03387g.
We describe the construction of synthetically challenging heteroleptic complexes by capitalizing on the solubility properties of their corresponding favored homoleptic complexes. We demonstrate that the formation of a heteroleptic Cu complex based on 2,2':6',2''-terpyridine (Terpy) and 8-hydroxyquinoline (HQ) is not possible due to the insolubility of (HQ)Cu. Replacing HQ with 8-hydroxy-2-quinolinecarbonitrile (HQCN) enabled the solubility of (HQCN)Cu in acetonitrile, leading to the formation of the heteroleptic complex Terpy(HQCN)Cu, TQCu. Applying these conditions to the synthesis of the corresponding heteroleptic Co complex resulted in TerpyCo(acetate), which is insoluble in acetonitrile. Upon changing the solvent to methanol, the carbonitrile group of HQCN was converted to carboxyimidate HQOMe yielding a heteroleptic complex Terpy(HQOMe)Co, TQ'Co. Using this method, we also generated the heteroleptic complex TQ'Ni and the polynuclear heteroleptic complex Q'4Q''2Mn4 (Q'' = HQOMe). Detailed analysis of the complexes included characterization by X-ray diffraction, EPR, UV-Vis, high resolution ESI MS, DFT calculations and electrochemistry. X-ray analysis of TQCu revealed distorted square pyramidal geometry, while TQ'Co and TQ'Ni exhibit distorted octahedral geometry, which includes metal coordination via the carboxyimidate nitrogen site. Interestingly, Q'4Q''2Mn4 was found to contain a [Mn(μ-O)(μ-O)N] core, which adopts a distorted octahedral geometry, and two types of HQ chelators. Thus, Q'4Q''2Mn4 is also heteroleptic even though it does not contain a Terpy ligand. Solution studies revealed that while TQCu is stable in solution, TQ'Co and TQ'Ni go through ligand exchange and are partially converted to their corresponding homoleptic complexes. Based on these data we could propose a mechanism for the formation of TQ'Co and TQ'Ni and show that TQ'Co can be prepared directly from Terpy and HQOMe.
我们利用相应的优势同配络合物的溶解性，描述了具有合成挑战性的异配络合物的构建。我们证明，由于（8 - 羟基喹啉）铜（(HQ)Cu）不溶，基于2,2':6',2'' - 三联吡啶（Terpy）和8 - 羟基喹啉（HQ）的异配铜络合物无法形成。用8 - 羟基 - 2 - 喹啉甲腈（HQCN）取代HQ，使得（HQCN）铜可溶于乙腈，从而形成异配络合物三联吡啶（8 - 羟基 - 2 - 喹啉甲腈）铜（Terpy(HQCN)Cu，TQCu）。将这些条件应用于相应异配钴络合物的合成，得到了不溶于乙腈的三联吡啶（乙酸根）钴（TerpyCo(acetate)）。将溶剂换成甲醇后，HQCN的腈基转化为羧基亚氨基酯HQOMe，生成异配络合物三联吡啶（8 - 羟基 - 2 - 喹啉甲氧基）钴（Terpy(HQOMe)Co，TQ'Co）。使用这种方法，我们还生成了异配络合物TQ'Ni和多核异配络合物Q'4Q''2Mn4（Q'' = HQOMe）。对这些络合物的详细分析包括通过X射线衍射、电子顺磁共振（EPR）、紫外 - 可见光谱（UV - Vis）、高分辨率电喷雾电离质谱（ESI MS）、密度泛函理论（DFT）计算和电化学进行表征。TQCu的X射线分析显示其几何形状为扭曲的四方锥，而TQ'Co和TQ'Ni呈现扭曲的八面体几何形状，其中包括通过羧基亚氨基酯氮位点的金属配位。有趣的是，发现Q'4Q''2Mn4包含一个[Mn(μ - O)(μ - O)N]核心，其采用扭曲的八面体几何形状，以及两种类型的HQ螯合剂。因此，即使Q'4Q''2Mn4不包含Terpy配体，它也是异配的。溶液研究表明，虽然TQCu在溶液中稳定，但TQ'Co和TQ'Ni会发生配体交换，并部分转化为它们相应的同配络合物。基于这些数据，我们可以提出TQ'Co和TQ'Ni的形成机制，并表明TQ'Co可以直接由Terpy和HQOMe制备。
